Many modern mobile devices, such as mobile smartphones, now have the ability to perform network scans to determine radio signal information, such as identifiers associated with nearby cellular base transceiver stations, WiFi™ access points and Bluetooth™ access points. Mobile devices may be further enabled to perform signal strength estimates and other signal measurements. Base transceiver stations and radio access points are primarily used for voice and data service access to the mobile device, but due to their relative permanence can be exploited for other purposes, including determining device location.
A number of approaches exist to translate signal information into location, including cell triangulation and trilateration techniques, such as Time Difference of Arrival (“TDOA”), Enhanced Observed Time Difference (“EOTD”), Advanced Forward Link Trilateration (“AFLT”) and Enhanced Cell Identification (“E-CID”). Such methods are considered terrestrial counterparts to the GPS satellite-based system which uses a form of triangulation based on satellite positioning.
In many environments it is difficult, if not impossible to directly use triangulation-type approaches against radio signals to determine a mobile device position. Particularly difficult environments typically include indoor environments, such as within office buildings or shopping malls, urban environments with high buildings, and rural environments with irregular terrain. In these environments, signal fade and signal multipath problems can make straightforward employment of signal triangulation unfeasible for determining mobile device location.
It may not be necessary for a particular location-based service application to have an exact ground truth location of a mobile device to provide specific content or services to a mobile device user. A particular location-based application may potentially function effectively given proper clues to a device's particular location even at times when a true location is not available for a particular mobile device. It would be desirable to provide a system and method by which mobile device users could receive location-based content without generating or providing an exact location with their mobile devices.